Method for mounting a heat exchanger device and a heat exchanger device

ABSTRACT

A method for assembling a heat exchanger device of a refrigeration unit may include pushing a heat exchanger coil of the heat exchanger device over a refrigerant collecting vessel of the heat exchanger device. The method may also include fluidically connecting the heat exchanger coil to the at least one cover of the heat exchanger device. The method may further include pushing a tubular casing of the heat exchanger device over the heat exchanger coil, and deforming the tubular casing radially inward.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to German Patent Application No. DE 10 2014 220 403.8, filed on Oct. 8, 2014, and International Patent Application No. PCT/EP2015/073023, filed on Oct. 6, 2015, both of which are hereby incorporated by reference in their entirety.

TECHNICAL FIELD

The invention relates to a method for assembling a heat exchanger device of a refrigeration unit. Furthermore, the invention relates to a heat exchanger device which is produced according to said method.

BACKGROUND

Heat exchanger devices of this type are used in refrigeration units, in particular in refrigeration units of an air conditioning system, for example a vehicle air conditioning system. By way of the use of said heat exchanger devices, the degree of efficiency of the refrigeration unit can be improved, in particular if CO₂ (R744) is used as refrigerant. By way of the heat exchanger device, the low temperature level of the low pressure region of the refrigeration circuit can be utilized, in order to further cool the warmer refrigerant in the high pressure region immediately downstream of the gas cooler. Here, the heat exchanger device can be combined with a refrigerant collecting vessel (accumulator). The integration of a heat exchanger coil with the refrigerant collecting vessel in one component is very complex and expensive, however.

DE 10 2006 031 197 A1 has disclosed an inner heat exchanger with an accumulator for refrigerant circuits, in particular in motor vehicle air conditioning systems, comprising a housing made from a pressurized tubular cylinder casing and a cover plate and a base plate, an accumulator which is made from a material which conducts heat poorly, preferably made from plastic, and is arranged so as to form a gap concentrically in the housing, for the liquid refrigerant at low pressure, and a finned tube for the refrigerant at high pressure, which finned tube is arranged in a helical manner in the gap between the accumulator and the cylinder casing. The cover plate and the base plate in each case have a connector plate with connectors for refrigerant lines, a U-shaped extraction tube with a vapor inlet and a vapor outlet for the refrigerant vapor being provided in the accumulator, and a baffle apparatus for separating the liquid and gaseous phase of the refrigerant being provided in the upper region of the accumulator. Here, the vapor inlet is arranged below the baffle apparatus in the accumulator in a manner which is protected against refrigerant liquid, and the vapor outlet is arranged outside the accumulator. The finned tube in turn is incorporated sealingly at its ends via a thread into the cover plate and the base plate, as a result of which an inner heat exchanger with an accumulator is to be provided, which heat exchanger can be produced cost-efficiently.

SUMMARY

The invention is based on the object of providing a heat exchanger device which combines an inner heat exchanger with a refrigerant collecting vessel and the assembly of which is simplified.

According to the invention, said object is achieved by way of the features of the independent claims. Advantageous embodiments are the subject matter of the dependent claims.

The invention is based on the general concept of mounting a housing of the heat exchanger device as last component, as a result of which the mounting of the heat exchanger coil and the refrigerant collecting vessel becomes simpler. Here, the heat exchanger coil is pushed over the refrigerant collecting vessel and is connected fluidically to the at least one cover, the tubular casing is pushed over the heat exchanger coil, and the tubular casing is deformed radially inward. As a result, the assembly and the connection between the at least one cover and the heat exchanger coil are simple, since the tubular casing of the housing does not block the access to the heat exchanger coil. Therefore, the selection of the connection between the heat exchanger coil and the at least one cover is not restricted. Furthermore, the connection of the refrigerant collecting vessel to the at least one cover and to the heat exchanger coil is simplified correspondingly.

It is favorable if the housing of the heat exchanger device has two covers, the heat exchanger coil is pushed over the refrigerant collecting vessel and is connected fluidically to the two covers, the tubular casing is pushed over at least one of the two covers and the heat exchanger coil, and, thereupon, the tubular casing is deformed radially inward. The flow paths in the heat exchanger device can be simplified as a result of the use of two covers. After the assembly of the heat exchanger coil and the refrigerant collecting vessel with the two covers, the tubular casing is then pushed over at least one of the two covers and is deformed radially inward. As a result, although the casing has to fit over at least one of the two covers, it can nevertheless have a functional smaller diameter after it has been deformed radially inward. Therefore, according to the invention, the assembly of the heat exchanger device can be improved without impairing the function of the heat exchanger device.

One advantageous solution provides that the tubular casing is deformed radially inward in such a way that it bears against the heat exchanger coil. By virtue of the fact that the tubular casing bears against the heat exchanger coil, a helical sealing face is formed which delimits a fluid duct which is, in particular, helical between the refrigerant collecting vessel and the tubular casing. Here, the helical fluid duct extends the dwell time in the heat exchanger device and improves the heat exchange as a result.

A further advantageous solution provides that the tubular casing is deformed radially inward hydraulically or pneumatically. In particular, a hydraulic or pneumatic deformation process brings about a homogeneous input of force into the tubular casing and therefore a homogeneous deformation process. A deformation process of this type can be applied in a flexible manner to different components, as a result of which tool costs can be reduced.

One particularly advantageous solution provides that the tubular casing is deformed radially inward by means of a forming tool. The deformation can be controlled precisely as a result of the use of a forming tool for deforming the tubular casing. In particular, it can be ensured in this way in an improved manner that the tubular casing bears against the heat exchanger coil without damaging the latter.

One advantageous possibility provides that the tubular casing is deformed radially inward to a more pronounced extent in the region of the heat exchanger coil than in the region of the cover. In this way, the advantages of the solution according to the invention can be utilized in a particularly favorable manner.

Another advantageous possibility provides that the tubular casing is deformed radially inward to a more pronounced extent in the region of the heat exchanger coil than in the region of the at least one cover. In this way, the advantages of the solution according to the invention can be utilized in a particularly favorable manner.

A further advantageous possibility provides that, before the tubular casing is pushed on, the refrigerant collecting vessel is connected to the two covers. As a result, the advantages according to the invention can also be utilized in the connection of the refrigerant collecting vessel to the two covers.

One favorable alternative provides that, before the deforming of the tubular casing, the latter is connected at least sealingly to the at least one cover. In this way, the cover and the tubular casing can form a fluid-tight housing. Furthermore, any type of connection can be used between the cover and the tubular casing.

Another favorable alternative provides that, before the deforming of the tubular casing, it is connected at least sealingly to both covers. In this way, the two covers and the tubular casing can form a fluid-tight housing. Furthermore, any type of connection can be used between the two covers and the tubular casing.

One advantageous alternative provides that the tubular casing is connected at least sealingly to the at least one cover by way of the deforming of the tubular casing. As a result, the tubular casing and the at least one cover form a fluid-tight housing, without it being necessary to provide further connecting means.

A further favorable alternative provides that the tubular casing is connected at least sealingly to both covers by way of the deforming of the tubular casing. As a result, the tubular casing and the two covers form a fluid-tight housing, without it being necessary to provide further connecting means.

Furthermore, according to the invention, the object is achieved by way of a heat exchanger device of a refrigeration unit having a housing which has at least one cover and a tubular casing, having a heat exchanger coil and having a refrigerant collecting vessel, the tubular casing being connected to the at least one cover, and the tubular casing being tapered at least on one side in a region between two ends of the tubular casing. This refinement makes it possible that the heat exchanger device is assembled in accordance with the preceding method, with the result that the advantages of the above-described method likewise extend to the heat exchanger device.

In the description and the appended claims, “to be tapered in a region” is understood to mean that the object has a smaller diameter, in particular internal diameter, in this region than in any other region of the object.

One advantageous variant provides that an internal diameter of the tubular casing is smaller in a region between two axial ends of the tubular casing than an internal diameter of the tubular casing at at least one of the two axial ends of the tubular casing. This refinement also makes it possible that the heat exchanger device is assembled in accordance with the preceding method, with the result that the advantages of the above-described method likewise extend to the heat exchanger device.

Furthermore, it is favorable if the housing of the heat exchanger device has two covers, if the tubular casing is connected to the two covers, and if the tubular casing is tapered at least on one side in a region between the two covers. This refinement makes it possible that a heat exchanger device having two covers is assembled in accordance with the preceding method, with the result that the advantages of the above-described method likewise extend to the heat exchanger device.

Furthermore, the abovementioned refinement of the heat exchanger device makes virtually any desired type of connection possible between the tubular casing and the two covers, since the connecting point is easily accessible.

A further advantageous variant provides that the internal diameter of the tubular casing is smaller in a region between two axial ends of the tubular casing than the internal diameter of the tubular casing at both axial ends of the tubular casing. This refinement also makes it possible that a heat exchanger device having two covers is assembled in accordance with the preceding method, with the result that the advantages of the above-described method likewise extend to the heat exchanger device.

One favorable solution provides that the tubular casing is in contact with at least one of the two covers or with the at least one cover exclusively by way of an inner side of the tubular casing. In this way, firstly the corresponding cover can be of simpler configuration. Secondly, the outer side of the tubular casing can be configured independently of restrictions as a result of the connecting capability to the cover. Therefore, costs can be spared.

One particularly favorable possibility provides that a refrigerant or a heat exchanger fluid is conducted through the heat exchanger coils, in particular under high pressure, and that the heat exchanger coil surrounds the refrigerant collecting vessel in a helical manner at least in sections. As a result, a second fluid passage which is different than the fluid passage within the heat exchanger coil is formed. In particular, said fluid passage is formed between the refrigerant collecting vessel and the tubular casing. On account of the helical course of the heat exchanger coil, said fluid passage likewise has a helical course, with the result that the heat exchanger coil and said fluid passage are guided on one another within the heat exchanger unit for a comparatively long distance. As a result, heat can be exchanged in a particularly satisfactory manner between the fluid which flows in the heat exchanger coil and fluid which flows in the fluid passage.

One favorable possibility provides that the at least one cover or both covers has/have an external diameter which is greater than an internal diameter of the tubular casing in a region between axial ends of the tubular casing. As a result, the two covers have a great cross-sectional area which can be used to attach refrigerant inlets and outlets and/or fastening means.

One particularly advantageous alternative provides that at least one of the two covers has an external diameter which is smaller than an internal diameter of the tubular casing before the deformation of the latter. As a result, the tubular casing can be pushed over said cover, with the result that it is made possible to first of all connect the heat exchanger coil, the refrigerant collecting vessel and the two covers to one another and subsequently to push on the tubular casing and to connect it to the remaining components.

It is particularly advantageous if the heat exchanger device has been assembled in accordance with the above-described method. The advantages of the method are therefore transferred to the heat exchanger device, reference being made to this extent to the above description of said method.

Further important features and advantages of the invention result from the subclaims, from the drawings and from the associated description of the figures using the drawings.

It goes without saying that the features which are mentioned above and are still to be described in the following text can be used not only in the respectively specified combination, but rather also in other combinations or on their own, without departing from the scope of the present invention.

Preferred exemplary embodiments of the invention are shown in the drawings and will be explained in greater detail in the following description, identical designations relating to identical or similar or functionally identical components.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, in each case diagrammatically:

FIG. 1 shows an outline sketch of a refrigeration unit,

FIG. 2 shows a sectional illustration through a heat exchanger device during assembly and before a tubular casing is pushed on,

FIG. 3 shows a sectional illustration of the heat exchanger device from FIG. 2, with the tubular casing which has been pushed on,

FIG. 4 shows a sectional illustration of the heat exchanger device from FIG. 3 after a deformation of the tubular casing,

FIG. 5 shows a sectional illustration of the heat exchanger device with arrows for identifying the refrigerant flow,

FIG. 6 shows a perspective view of a heat exchanger coil,

FIG. 7 shows an illustration of two possible cross sections of a tube of the heat exchanger coil, and

FIG. 8 shows an illustration of two further possible cross sections of a tube of the heat exchanger coil.

DETAILED DESCRIPTION

A refrigeration unit 10 which is shown diagrammatically in FIG. 1 comprises a compressor 12, a gas cooler 14, a heat exchanger device 16, a throttle or an expansion valve 18, and an evaporator 20. Here, the refrigeration unit 10 operates on the known principle of the refrigeration circuit. A refrigerant 22 passes through a circuit 28 which is driven by the compressor 12. First of all, the refrigerant 22 is compressed in the compressor 12, as a result of which the temperature of the refrigerant 22 is increased. From the compressor 12, the refrigerant 22 is guided into the gas cooler 14, where it can dissipate heat to the surroundings on account of the increased temperature as a result of the compression. From the gas cooler 14, the refrigerant 22 is guided via an inner heat exchanger 30 to the throttle/expansion valve 18 which throttles or regulates the flow of the refrigerant 22 and separates a low pressure region 24 from a high pressure region 26. Downstream of the throttle/expansion valve 18, the refrigerant 22 flows into the evaporator 20, in which it expands and is cooled in the process. By virtue of the fact that the refrigerant 22 can output heat to the surroundings in the high pressure region 26, the temperature of the refrigerant 22 is lower in the evaporator 20 than it was upon entry of the refrigerant 22 into the compressor 12. The evaporator 20 has a second flow path for a medium to be cooled, such as air, with the result that the refrigeration unit 10 can absorb heat from the medium to be cooled. A refrigerant collecting vessel 32 is arranged downstream of the evaporator 20, from which refrigerant collecting vessel 32 the refrigerant 22 is guided via the inner heat exchanger 30 to the compressor 12. The refrigeration unit 10 is used, for example, in air conditioning systems of motor vehicles.

On account of its lower greenhouse activity in comparison with other refrigerants, CO₂ (R744) is used as refrigerant 22. In particular, if CO₂ is used as refrigerant 22, the use of the inner heat exchanger 30 is favorable for the degree of efficiency of the refrigeration unit 10. Via the inner heat exchanger 30, heat from the refrigerant 22 in the high pressure region 26, in particular downstream of the gas cooler 14, is transferred to the refrigerant 22 in the low pressure region 24, in particular downstream of the throttle/expansion valve 18. As a result, the temperature of the refrigerant 22 can be reduced still further at the throttle/expansion valve 18, with the result that the degree of efficiency of the refrigeration unit 10 is improved.

To this end, the refrigeration unit 10 has the heat exchanger device 16 according to the invention which comprises the inner heat exchanger 30 and the refrigerant collecting vessel 32. Both are arranged in a housing 34 which has at least one, for example two, covers 36 and a tubular casing 38. Two fluid ducts run within the housing 34. A first fluid duct 40 is formed by the inner heat exchanger 30, in particular by a heat exchanger coil 42 of the inner heat exchanger 30. A second fluid duct 44 extends within the housing 34 and in the process runs through the refrigerant collecting vessel 32 and through a region between the refrigerant collecting vessel 32 and the tubular casing 38. The heat exchanger coil 42 of the inner heat exchanger 30 also runs in said region (cf. FIGS. 4, 5).

The two fluid ducts 40, 44 are connected in such a way that the two fluid ducts 40, 44 are flowed through in counterflow in the region between the refrigerant collecting vessel 32 and the tubular casing 38, and the heat can thus be transmitted particularly effectively from the one fluid duct to the other fluid duct.

For example, the first fluid duct 40 and therefore the heat exchanger coil 42 are flowed through by refrigerant 22 from the high-pressure region 26 in a manner which comes from the gas cooler 14, whereas the second fluid duct 44 is flowed through by refrigerant 22 from the low pressure region 24 in a manner which comes from the evaporator 20 or the refrigerant collecting vessel 32. The heat of the refrigerant 22 from the high pressure region 26 can thus dissipate to the refrigerant 22 on the low pressure side.

The heat exchanger coil 42 runs in a helical manner at least in sections through the housing 34 of the heat exchanger device 16. In particular, the heat exchanger coil 42 runs in a helical manner in a cylindrical casing-shaped region between the refrigerant collecting vessel 32 and the tubular casing 38. The heat exchanger coil 42 preferably bears against the tubular casing 38, with the result that a helical sealing face is produced between the heat exchanger coil 42 and the tubular casing 38.

As a result, the heat exchanger coil 42 surrounds the refrigerant collecting vessel 32. Here, the heat exchanger coil 42 can likewise bear against the refrigerant collecting vessel 32, with the result that the second fluid duct 44 extends in a helical manner between the refrigerant collecting vessel 32 and the tubular casing 38 and thus has a great length and the refrigerant 22 has a comparatively great amount of time to absorb heat from the heat exchanger coil 42. As an alternative, there can be a spacing between the heat exchanger coil 42 and the refrigerant collecting vessel 32. As a result, the second fluid duct 44 is not of helical configuration in the region between the refrigerant collecting vessel 32 and the tubular casing 38, but the heat exchanger coil 42 produces a finned or corrugated surface, with the result that the fluid 22, when it flows through the second fluid duct 44, is swirled and can absorb heat from the heat exchanger coil 42 effectively as a result. This second variant has a lower flow resistance than the first variant. However, the thermal coupling between the second fluid duct 44 and the first fluid duct 40 is correspondingly lower. The possibility is offered to adapt the heat coupling and flow resistance to the respective requirements in an optimum manner.

The heat exchanger coil 42 is connected to refrigerant connectors in the covers 36, with the result that the refrigerant 22 can be guided through the heat exchanger coil 42 by way of the refrigerant connectors in the covers 36.

As shown, for example, in FIGS. 6, 7 and 8, the heat exchanger coil 42 can have various cross sections; in particular, the heat exchanger coil 42 can have circular, oval or elliptic cross sections. As an alternative or in addition to this, the heat exchanger coil 42 can also have a relatively flat profile with a plurality of relatively small individual ducts 50 within the heat exchanger coil 42.

The refrigerant collecting vessel 32 serves to catch and collect gaseous or liquid refrigerant 22 from the refrigerant gas flow and therefore to form a type of cooling reservoir. To this end, the refrigerant collecting vessel 32 has a cylindrical main body, through which the refrigerant 22 is introduced approximately axially in a manner which comes from the evaporator 20. A further opening is situated on the same side, through which further opening the gaseous refrigerant 22 can flow out of the refrigerant collecting vessel 32 again. As a result, the refrigerant 22, after flowing into the refrigerant collecting vessel 32, has to pass through an arc, by way of which liquid or solid parts of the refrigerant 22 are deposited.

Accordingly, the refrigerant collecting vessel 32 is connected to at least one of the covers 36, with the result that refrigerant 22 can flow in through a refrigerant inlet in the refrigerant collecting vessel 32.

The mounting of the refrigerant collecting vessel 32 and the heat exchanger coil 42 onto the covers 36 would be made more difficult if the tubular casing 38 were already connected to one of the covers 36. For this reason, the tubular casing 38 is configured in such a way that it can be mounted as last part of the heat exchanger device 16.

As a result, the connection between the covers 36 and the refrigerant collecting vessel 32 and the connection between the covers 36 and the heat exchanger coil 42 can be carried out in a very simple manner, with the result that connecting possibilities which are favorable and/or particularly advantageous in some other way can also be applied. In particular, there is no restriction with regard to the connection type between the covers 36 and the heat exchanger coil 42 and the refrigerant collecting vessel 32.

The tubular casing 38 first of all has an internal diameter 46 which is greater than an external diameter 48 of the covers 36 (cf. FIG. 3). As a result, the tubular casing 38 can be pushed over the two covers 36. It is sufficient here if the tubular casing 38 can be pushed merely over one of the two covers 36. As a consequence, one of the two covers 36 can have an external diameter 48 which is greater than the internal diameter 46 of the tubular casing 38.

An alternative or an addition to this is a configuration of the heat exchanger device 16 with only one cover which has all necessary refrigerant connectors, and a tubular casing 38 which is closed on one side. It is sufficient here if the internal diameter 46 of the tubular casing 38 is greater than an external diameter of the heat exchanger coil 42, with the result that the tubular casing 38 can be pushed over the heat exchanger coil 42 and onto the cover 36.

Since the tubular casing 38 is to be in contact with the heat exchanger coil 42, the tubular casing 38 is deformed radially inward (cf. FIG. 4) after being pushed onto the heat exchanger device 16. By way of said radial deformation process, the tubular casing 38 can also be connected in a fluid-tight manner to the covers 36. As an alternative, the tubular casing 38 can also be connected to the covers 36 before the radial deformation operation.

The radial deformation of the tubular casing 38 can be achieved, for example, by way of hydraulic or pneumatic pressure which is applied to the tubular casing 38 from the outside. As an alternative or in addition to this, the radial deformation of the tubular casing 38 can be carried out by way of a forming tool.

As a result of this sequence of assembly, the connection of the covers 36 to the heat exchanger coil 42 and the refrigerant collecting vessel 32 is not disrupted by the tubular casing 38 and the assembly of the heat exchanger device 16 is considerably facilitated.

After the radial deforming of the tubular casing 38, the internal diameter 46 of the tubular casing 38 is reduced in a region 45 between two axial ends 47 of the tubular casing 38. As a result, the tubular casing 38 can bear against the heat exchanger coil 42. The diameter 48 of the at least one cover 36 is greater than the diameter of the heat exchanger coil 42. As a consequence, the internal diameter 46 of the tubular casing 38 is greater at the axial ends 47 than in the region 45 between the axial ends 47. 

1. A method for assembling a heat exchanger device of a refrigeration unit, the heat exchanger device having a housing with at least one cover and a tubular casing, a heat exchanger coil, and a refrigerant collecting vessel, the method comprising: pushing the heat exchanger coil over the refrigerant collecting vessel; fluidically connecting the heat exchanger coil to the at least one cover; pushing the tubular casing over the heat exchanger coil; and deforming the tubular casing radially inward.
 2. The method as claimed in claim 1, wherein: the housing includes two covers; fluidically connecting the heat exchanger coil to the at least one cover includes fluidically connecting the heat exchanger coil to the two covers; and the method further includes pushing the tubular casing over at least one of the two covers in addition to the heat exchanger coil.
 3. The method as claimed in claim 1, wherein deforming the tubular casing is performed in such a way that the tubular casing bears against the heat exchanger coil.
 4. The method as claimed in claim 1, wherein deforming the tubular casing radially inward is performed one of hydraulically, pneumatically, or via a forming tool.
 5. The method as claimed in claim 1, wherein deforming the tubular casing radially inward includes deforming the tubular casing to a greater extent in a region of the heat exchanger coil than in a region of the at least one cover.
 6. The method as claimed in claim 1, further comprising one of: connecting the tubular casing at least sealingly to the at least one cover before deforming the tubular casing; and connecting the tubular casing at least sealingly to the at least one cover concurrently with deforming the tubular casing.
 7. A heat exchanger device of a refrigeration unit, comprising: a housing with at least one cover and a tubular casing, the tubular casing connected to the at least one cover; a heat exchanger coil; and a refrigerant collecting vessel; wherein the tubular casing is tapered at least on one side in a region between two ends of the tubular casing.
 8. The heat exchanger device as claimed in claim 7, wherein an internal diameter of the tubular casing is smaller in a region between two axial ends of the tubular casing than an internal diameter of the tubular casing at at least one of the two axial ends.
 9. The heat exchanger device as claimed in claim 7, wherein: the housing includes two covers; the tubular casing is connected to the two covers; and the tubular casing is tapered at least on one side in a region between the two covers.
 10. The heat exchanger device as claimed in claim 9, wherein an internal diameter of the tubular casing is smaller in a region between two axial ends of the tubular casing than an internal diameter of the tubular casing at both axial ends.
 11. The heat exchanger device as claimed in claim 7, wherein the tubular casing contacts the at least one cover exclusively on an inner side of the tubular casing.
 12. The heat exchanger device as claimed in claim 7, wherein: one of a refrigerant and a heat exchanger fluid flows in the heat exchanger coil under high pressure; and the heat exchanger coil surrounds at least sections of the refrigerant collecting vessel in a helical manner.
 13. The heat exchanger device as claimed in claim 7, wherein the at least one cover includes an external diameter that is greater than an internal diameter of the tubular casing in a region between two axial ends of the tubular casing.
 14. The heat exchanger device as claimed in claim 7, wherein: the heat exchanger coil is arranged over the refrigerant collecting vessel and fluidically connected to that at least one cover; the tubular casing is arranged over the heat exchanger coil; and the tubular casing is deformed radially inward.
 15. The heat exchanger device as claimed in claim 9, wherein the tubular casing contacts at least one of the two covers exclusively on an inner side of the tubular casing.
 16. The heat exchanger device as claimed in claim 9, wherein one of a refrigerant and a heat exchanger fluid flows in the heat exchanger coil under high pressure, and the heat exchanger coil surrounds at least sections of the refrigerant collecting vessel in a helical manner.
 17. The heat exchanger device as claimed in claim 9, wherein at least one of the two covers includes an external diameter that is greater than an internal diameter of the tubular casing in a region between two axial ends of the tubular casing.
 18. The heat exchanger device as claimed in claim 14, wherein an internal diameter of the tubular casing is smaller in a region between two axial ends of the tubular casing than an internal diameter of the tubular casing at at least one of the two axial ends.
 19. The heat exchanger device as claimed in claim 14, wherein the tubular casing contacts the at least one cover exclusively on an inner side of the tubular casing.
 20. A heat exchanger device comprising: a housing with at least one cover and a tubular casing, the tubular casing connected to that at least one cover such that the tubular casing contacts that at least one cover exclusively on an inner side of the tubular casing; a refrigerant collecting vessel; and a heat exchanger coil configured to surround at least sections of the refrigerant collecting vessel in a helical manner; wherein the tubular casing is tapered at least on one side in a region between two axial ends of the tubular casing. 